Rat liver insulin receptor

Journal Article · Mon Nov 16 23:00:00 EST 1987 · Biochemistry; (United States)

DOI:https://doi.org/10.1021/bi00397a028· OSTI ID:5301683

Hofmann, K; Romovacek, H; Titus, G; Ridge, K; Raffensperger, J A; Finn, F M

Using insulin affinity chromatography, the authors have isolated highly purified insulin receptor from rat liver. When evaluated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis under reducing conditions, the rat liver receptor contained the M/sub r/ 125,000 ..cap alpha..-subunit, the M/sub r/ 90,000 ..beta..-subunit, and varying proportions of the M/sub r/ 45,000 ..beta..'-subunit. The specific insulin binding of the purified receptor was 25-30 ..mu..g of /sup 125/I-insulin/mg of protein, and the receptor underwent insulin-dependent autophosphorylation. Rat liver and human placental receptors differ from each other in several functional aspects: (1) the adsorption-desorption behavior from four insulin affinity columns indicated that the rat liver receptor binds less firmly to immobilized ligands; (2) the /sup 125/I-insulin binding affinity of the rat liver receptor is lower than that of the placental receptor; (3) partial reduction of the rat liver receptor with dithiothreitol increases its insulin binding affinity whereas the binding affinity of the placental receptor is unchanged; (4) at optimal insulin concentration, rat liver receptor autophosphorylation is stimulated 25-50-fold whereas the placental receptor is stimulated only 4-6-fold. Conversion of the ..beta..-subunit to ..beta..' by proteolysis is a major problem that occurs during exposure of the receptor to the pH 5.0 buffer used to elute the insulin affinity column. Proteolytic destruction and the accompanying loss of insulin-dependent autophosphorylation can be substantially reduced by proteolysis inhibitors. In summary, rat liver and human placental receptors differ functionally in both ..cap alpha..- and ..beta..-subunits. Insulin binding to the ..cap alpha..-subunit of the purified rat liver receptor communicates a signal that activates the ..beta..-subunit; however, major proteolytic destruction of the ..beta..-subunit does not affect insulin binding to the ..cap alpha..-subunit.

• Research Organization: Univ. of Pittsburgh School of Medicine, PA
• OSTI ID: 5301683
• Journal Information: Biochemistry; (United States), Journal Name: Biochemistry; (United States) Vol. 26:23; ISSN BICHA
• Country of Publication: United States
• Language: English

Related Subjects

550601* -- Medicine-- Unsealed Radionuclides in Diagnostics
62 RADIOLOGY AND NUCLEAR MEDICINE
ANIMALS
ATP
AUTORADIOGRAPHY
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
BODY
CHEMICAL ACTIVATION
CHEMICAL REACTIONS
DAYS LIVING RADIOISOTOPES
DIGESTIVE SYSTEM
ELECTRON CAPTURE RADIOISOTOPES
ELECTROPHORESIS
FETAL MEMBRANES
GLANDS
HORMONES
INSULIN
INTERMEDIATE MASS NUCLEI
IODINE 125
IODINE ISOTOPES
ISOTOPE APPLICATIONS
ISOTOPES
LIGANDS
LIGHT NUCLEI
LIVER
MAMMALS
MAN
MEMBRANE PROTEINS
MEMBRANES
NUCLEI
NUCLEOTIDES
ODD-EVEN NUCLEI
ODD-ODD NUCLEI
ORGANIC COMPOUNDS
ORGANS
PEPTIDE HORMONES
PHOSPHORUS 32
PHOSPHORUS ISOTOPES
PHOSPHORYLATION
PLACENTA
PRIMATES
PROTEINS
RADIOISOTOPES
RADIORECEPTOR ASSAY
RATS
RECEPTORS
RODENTS
TRACER TECHNIQUES
VERTEBRATES